Electro-mechanical switches have become extremely important to provide user control of various features and functions of electronic and micro-electronic devices, such as hearing aids. Push button switches are typically utilized in applications that require simple on/off functionality. Such switches can be normally open (i.e., actuation of the switch closes an associated circuit) or normally closed (i.e., actuation of the switch opens an associated circuit). While push button switches are utilized in simple on/off applications, their implementation and design are not always simple.
Push button switches typically have an actuator, driver, or plunger of some type that is situated within a switch housing having at least two contacts in communication with an electrical circuit within which the switch is incorporated. A user can depress the plunger to actuate the switch by either causing the contacts to make contact with each other (normally open switch) or break contact with each other (normally closed switch). An actuation point is defined as the point where the switch causes the contacts to either first contact each other or first break contact with each other. Because of manufacturing and assembly tolerances, this actuation point can vary from switch to switch. To address the effects of assembly tolerances, as well as issues concerning user “feel” of the switch, push button switches are typically designed with an over-travel component, wherein the plunger is allowed to travel past the actuation point. Thus, a user is allowed to continue to depress the plunger even after the switch is actuated.
One known push button switch having an over-travel mechanism includes a pair of springs disposed on an axis of the plunger. The first spring appears to provide the bias force against which the plunger is depressed. The actuator is depressed when the actuation force overcomes the spring force of this first spring. Once the switch is actuated, the second spring appears to compress and provide the over-travel component. One problem with this configuration is the dependence on the spring constants. A small change in either spring may result in the elimination of the over-travel component.
Other problems associated with known push button switches having over-travel components and actuation points include lack of control in defining the point of actuation and the amount of over travel, as well as a general lack of robustness and reliability in their designs such that the switches can withstand repeated use.
The present invention is provided to solve these and other problems.